The old bearings collapsed when taking them out rollers everywhere,
The outer is a plain roller, and although rollers caged, it's a very loose cage, so can easily do that, whilst having been OK in operation (but may not have been) The inner race is separate and as you say may not slide easily up the shaft
You need the axle upright (fixed) and lower the hub onto it, with 3 hands (!) drifting v.carefully the inner race down the shaft if necessary, long thin drift or thinwalled tube, no jumpy off into cage (or jolt it down by dropping whole assembly onto axle flange a few times, hardwood/dead square of course

. Then drop the spacer down, fill void with grease as far as poss, then making sure all the rollers are stuck back out of the way with grease, slide the inner race into place, use a collar/thinwalled tube or drift if necessary. Don't let it come back out before now fitting the drive flange
I doubt that will help much, but sometimes it easy soemtimes I varied method, but that seemed the best way when things got all greasy and difficult. I wouldn't emery the shaft much, just clean it but you could freeze it first with that coldfreeze spray.
3rd time lucky
